280 Bulletin American Museum of Natural History. [Vol. XXXIV, 
Genus Simosciurus gen. nov. 
Text Fig, 12 (p. 164); Plate XII, Figs. 1-38; Plate XIV, Figs. 5, 6. 
Type, Sciurus stramineus Eydoux and Souleyet. 
Size large; tail long and narrow, the vertebra about 52 % of the total 
length; mamme, 8; pelage very long and thick. 
Premolars, +. Skull short, due mainly to the extremely short rostrum; 
nasals very broad and short, about 22 % of the total length of the skull, and 
only about 60 % of the interorbital breadth instead of 90 % as in Urosciurus; 
dorsal profile flattened and nearly straight over the mid-dorsal half of the 
skull as in Uroscvwrus, not highly convex as in the small and medium-sized 
South American squirrels; zygomata slightly convergent anteriorly; malar 
broad and heavy, without superior expansion; dentition of rather more 
than medium strength, similar in structural details to that of the other 
large South American squirrels. 
Geographic distribution. Southwestern Ecuador and northwestern 
Peru. (See map, p. 300.) 
Remarks.— The distinctive features of S¢moscturus are the extremely 
short rostrum, giving the skull a peculiar snub-nosed effect, the correlatively 
very short and broad nasals, and the heavily developed zygomata. While 
_ the tail is long, the numerous specimens at hand show it to be narrow and 
lightly haired in comparison with Hadroscturus and Urosciurus. The genus 
is thus far represented by only Sciurus stramineus and its several subspecies, 
geographically restricted to a comparatively limited area in southwestern 
Ecuador and northwestern Peru bordering the Gulf of Guayaquil. 
Species and Subspecies of Simosciurus, with type localities and statement of 
number of specimens examined. 
Simosciurus stramineus stramineus (Eydoux and Souleyet). Omatope, 
Peru. Specimens examined, 8. 
Simosciurus stramineus nebouxii (I. Geoffroy). Near Payta, Peru. 
Specimens examined, 5. 
Simosciurus stramineus guayanus (Thomas). Balzar Mountains, west- 
ern Ecuador. Specimens examined, 0. 
Simosciurus stramineus zarume (Allen). Zaruma, southwestern Ecua- 
dor. Specimens examined, 1. | 
Key to the Subspecies of Simosciurus. 
With a nuchal white patch. 
Upperparts yellowish gray, underparts whitish gray...... nebouxit (p. 282) 
Upperparts deep yellowish rufous, underparts brownish gray. .zarume (p. 284) 
